1. Technical Field of the Invention
The present invention relates to temperature alarm circuitry, and more particularly to a temperature alarm circuit useful in a tamper detection circuit.
2. Description of Related Art
There exist electronics systems in which very sensitive data may be stored in an integrated circuit (IC). For example, some portable credit card scanners store credit card data in volatile memory which, if pilfered, would potentially expose credit card holders to credit card fraud.
In an effort to prevent such pilfering of data, techniques exist for detecting when an IC or system is being tampered with, and destroying the stored data in response to the detection. In this way, sensitive data stored in such systems remains inaccessible.
One known way of attempting to improperly access stored data is to subject the IC or system to changes in temperature, for example by exposing the IC or system to extreme heat or extreme cold. There is accordingly a need for a type of tamper detection which involves detecting whether the temperature of the IC or system falls outside an expected operating range (for example, too hot or too cold in comparison to certain temperature thresholds), and asserting an alarm responsive to such detection. Such a temperature tamper detector would serves the purpose of preventing a tamperer from accessing stored, sensitive data in part by the tamperer changing the operating temperature of the IC or system.